The general chemical formula of ideal inorganic perovskite is ABX3, in which, the central metal cationic B and anion X form an octahedral structure. A filled in gaps of the octahedral structure is configured for equilibrating charge of the anion BX3. For a typical three-dimensional perovskite structure, when extracting several octahedral layers from the three-dimensional structure along a certain direction, or replacing several octahedral layers with other components, then layered perovskite structure could appear. Organic-inorganic hybridized perovskite material is formed by replacing atoms at A site on the inorganic perovskite with organic amine, the organic amine is filled in gaps of each octahedral structure. Octahedral structures may be connected with each other to form a network structure via a common vertex. The organic amine may enter into the inorganic spatial by means of hydrogen bonds formed by hydrogens at the organic amine and halide ions. The organic chains are interacted with each other by Van Der Waals force to form a hybrid structure having alternating organic and inorganic layers. For the hybridized perovskite structure, the organic amine filled in the gaps of the inorganic octahedral structure needs to satisfy the restriction of the tolerance factor t: (RA+RX)=t√2(RB+RX), RA is radius of A atoms, RB and RX are radii of corresponding element atoms. When the tolerance factor t is in the range of 0.8≤t≤0.9, the three-dimensional perovskite structure is formed. Therefore, the radii of A. B and X atoms determine whether the organic amine chains can be filled in the gaps. For the hybridized perovskite structure in which the lead halide and tin halide form inorganic layers, being capable of forming the three-dimensional structure of short-chain amine, such as CH3NH3MX3(M=Pb, Sn) and NH2CH═NH2SnI3.
Organic-inorganic hybridized perovskite material combines the advantages of organic materials and inorganic materials on the molecular scale, not only having good thermal stability, mechanical property and electromagnetic property of the inorganic materials, but also being easily processed into a film. A quantum well structure is formed by alternately stacking the unique inorganic and organic layers of the organic-inorganic hybridized perovskite material enable the hybridized perovskite material to have a relatively high excitation binding energy under dual effects of the quantum confinement and electric confinement, with the features of showing a distinct optical characteristics such as high charge carrier mobility and strong room-temperature photoluminescence, and having a relatively narrow half-peak width and high luminous purity. Furthermore, by controlling amount of organic materials and inorganic materials, the luminescence property of the hybridized perovskite material can be controlled. Therefore, the hybridized perovskite material has unique application value in the fields of field effect transistors, solar batteries, electro-luminescence, display devices and so on. Because of the unique property and application value of the hybridized perovskite material, the research on this kind of material has been drawn wide attention of researchers in recent years.
When size of the organic-inorganic hybridized perovskite material is decreased to the nanometer scale, because quantum dot has a small size and owns surface ligands, the quantum dot may easily diffuse into common solutions, enabling the hybridized perovskite material to be processed and applied easily. Therefore, the hybridized perovskite material may be applied in electro-optic fields through various ways. Meanwhile, due to its quantum confinement effect of the quantum dot, the organic-inorganic hybridized perovskite quantum dot shows more excellent property than bulk materials, such as a stronger luminescence intensity and higher quantum yield, and its luminescence wavelength can be adjusted by controlling the size of namo-particles. Compared to inorganic quantum dot material, the half-peak width of the organic-inorganic hybridized perovskite quantum dot is narrower and its luminescence purity is higher, which has big advantages in high performance display devices. The hybridized perovskite material could be a potential material for making laser. Additionally, its layered self-assembly structure enables the hybridized perovskite material to own distinct nonlinear optical property, which can be applied into nonlinear optical devices. Therefore, the organic-inorganic hybridized perovskite quantum dot material owns a vital position in the field of the hybridized perovskite material.
Currently, the preparation method of the organic-inorganic hybridized perovskite quantum dot is less to be reported. The hybridized perovskite quantum dot was manufactured by template method before. In 2012, Akihiro Kojima et al. reported using porous alumina template to synthesize nanostructure CH3NH3PbBr3 in Chemistry Letters. The method is injecting a precursor solution into nano-scale pores of the porous alumina template, the growth of CH3NH3PbBr3 particles are restricted by use of the nano-scale pores to obtain CH3NH3PbBr3 quantum dot with luminescence wavelength at 523 nm. Even though using the method can make CH3NH3PbBr3 quantum dot, the CH3NH3PbBr3 quantum dot is embedded in the aluminum oxide template and not suitable for future processing and application to devices. In 2014, Luciana C. Schmidt first reported using non-template method to make nanostructure CH3NH3PbBr3 on the Journal of American Chemistry Society. The method is using ODE (1-octadecene) as the solution, under the reaction temperature 80° C. adding methyl ammonium bromide salts, long-chain amine bromide salts, lead bromide etc, dispersing the above-mentioned materials into the solution uniformly, finally adding acetone thereto, then the CH3NH3PbBr3 particles are obtained via precipitation method. If the CH3NH3PbBr3 particles with luminescence wavelength at 526 nm, the fluorescence quantum yield reaches to 20%. However, the hybridized perovskite quantum dot material still has a low fluorescence quantum yield. The dispersibility of quantum dot in solutions still needs to be improved. Nowadays, reports on the hybridized perovskite quantum dot material still focus on CH3NH3PbBr3 quantum dot with luminescence wavelengths in the range of 520-530 nm, the adjustment of the luminescence wavelength is very narrow.
Therefore, even though the perovskite quantum dot material exhibits the photoluminescence property and excellent optoelectronic property at the room temperature, the perovskite quantum dot material still has a low quantum yield. It is difficult for the perovskite quantum dot material to disperse into solutions, meanwhile to prevent the structure from damage, which becomes one bottleneck that limits the development of the perovskite quantum dot material. Accordingly, improving the fluorescence quantum yield of the perovskite quantum dot material and obtaining good dispersibility of perovskite solutions seem especially important.